Production of hydrogen-rich liquid fuels from coal



Jan. 23, 1962 E. GoRlN 3,018,241

PRODUCTION 0F HYDROGEN-RICH LIQUID FUELS FROM COAL Filed Oct. 10, 1960 f 3 Sheets-Sheet l I I l I l l I l Q N vo v Q INVENTOR Enf-'R577' 60k/N E. GORIN Jan. 23, 1962 PRODUCTION OF' HYDROGEN-RICH LIQUID FUELS FROM COAL 3 Sheets-Sheet 2 Filed Oct. l0, 1960 E. GoRlN 3,018,241

PRODUCTION oF HYDRoGEN-RICH LIQUID FUELS' FROM COAL Jan. 23, 1962 3 Sheets-Sheet 3 Filed Oct. 10, 1960 NEON WON

IN VEN TUR.

TT/VEV EVRETT 60E/N United States Patent O PRODUCTION F HYDROGEN-RICH LIQUID FUELS FROM COAL Everett Gorin, Pittsburgh, Pa., assignor .to Consolidation Coal Company, Pittsburgh, Pa., a corporation of Penn- Sylvania Filed Oct. 10, 1960, Ser. No. 61,517 5 Claims. (Cl. 208-8) Yeach of the above `'applications being assigned to the aS- vsignee of the present invention.

Of the many processes that have been proposed for conversion of coal to gasoline, those which involve only partial conversion of the carbon content of the coal to liquids are the most attractive economically. Any attempt to convert all the carbon of the coal to hydrocarbons must of necessity include the addition of large quantities of extrinsic hydrogen. Such addition is obviously expensive in view of the high cost of hydrogen. This is the major reason why there is no commercial coal-to- Vgasoline plant in this country today.

On the other hand, partial conversion of coal to liquid form offers attractive possibilities of making coal-to-gasoline plants a reality in the U.S. economy. The concept of partial conversion implies that optimum use is made .of the hydrogen that is already present in the gross coal whereby it is preferentially distributed to a portion of the carbon content, leaving a hydrogen depleted residue. The generally yaccepted practical embodiment .of partial conversion is low temperature carbonization, i.e. distillation of the coal in the temperature range .of V.about 425 C. to 760 C. From such rlow temperature carbonization, a liquid, i.e. tar, is obtained which is hydrogen-,rich in. contrast to the Vsolid residue, i.e. char which zis Vhydrogendepleted, as illustrated in the following Table I wherein the ultimate analyses in percent by weight are given on a moisturefree and ash-free basis (i.e. maf.) for the tar and char respectively obtained by the carbonization of a PittsburghSeam coal at 496 C.

TABLE I Char Tar H 3.a 7.a .C t 87.0 `83. 4 O v ,3. 7 6. 3 N- -1:8 V1:0 l Y Y4.2 2.o

The liquid .product of low temperature carbonization of coal, because of its hydrogen-rich character, has been ICC at comparable cost because of the necessity Vfor preventing agglomeration of the coal in the carbonization vessel. By way of illustration, the potential yield of tar from 'a highly caking coal of the Pittsburgh Seam, ,as determined by carbonization of the coal in the presence of sufhcient inert diluent to prevent agglomeration, is in the range `of 20 to 25 percent by weight of the m.a.f. coal. lIn acontinuous process employing oxygen to de-cake the coal, the yield of tar drops to the range .of 1 0 to 15 percent Tby weight of the maf. coal. Thus, not only has the yield of the desired product been substantially reduced, but also the cost, because of the de-caking step, has increased.

The extraction of coal by means of solvents has been proposed as a kind of partial conversion of the coal. In some instances extraction has been accompanied by'concurrent hydrogenation as by the use of extrinsic hydrogen, or by concurrent deposition of coke. The difficulty with such concurrent addition of hydrogen or concurrent rejection of carbon in the form .of coke is that both are relatively non-selective, that is, not only is the .extract subjected to such treatment, but so also is the coal residue. Thus, uncontrolled, indiscriminate, and ineicient `redistribution of hydrogen is effected.

Coal extracts contain too many lcompounds vof widely dierent molecular size to permit complete resolution Qf their component molecular species. However, it is ,asuicient for present purposes to examine `the gross characteristics of the extracts in terms of molecular weight. Using benzene as a solvent, l have found that coal extracts may be separated readily into two fractions, a benzene-,soluble and a benzene-insoluble,fraction respectively. Surprisingly, the benzene-insoluble fraction has the following characteristics, set forth in Table II, regardless of the .conditions, solvent used, or depth of extraction Vemployed in the initial solvent extraction treatment.

TABLE II Average molecular weight 7. 1500 Melting temperature range 250 VC.350 C. Hydrogen (wt. percent) 5.5 `to 6.'0

The ventire ultimate analysis of the benzene-insolubles is similar to that of the vfeed coal except as to oxygen and sulfur. The benzene-solubles, on the other hand, vary in their characteristics depending on Vthe `conditions of extraction. In general, however, their molecular weight ranges from 300 to 1000; Vand their hydrogen content ranges from 6 to 8 percent by weight.

While the characteristics of the benzene-insoluble fraction of the extract, as set forth above, ,do `not change significantly with increasing coal extraction, the amount of this portion Vin the extract increases `materially with increasing coal extraction, in the absence of cok'ing or hydrogen addition during .the solvent extractiOu.` This increase in amount of benzene-insolubles was observed in the case of all solvents tried, but at different rates of increase. I have further found that as the 'benzene-irisoluble Vfraction of extract increases, the extract becomes correspondingly more diflicult to hydrogenate, i.e., higher temperatures and pressures are required to convert substantially all the extract to hydrogen-enriched hydrocarbonaceous liquid. i

The primary object of the present .invention vi s 'to Vprovide an improved process for converting bituminous coal, and particularly a highly lcaking bituminous coal, to a hydrogen-enriched liquid suitable as feedstock 'for gasoline manufacturing operations.

Another object of this invention is to provide a com- .and temperatures.

bination process for converting coal to a gasoline feedstock which process combines, to best advantage in selective fashion, low temperature carbonization, solvent extraction, coking of liquids, and hydrogenation.

A further object of this invention is to provide a process for producing a hydrogen-enriched liquid suitable as a gasoline feedstock, which process comprises hydrogenating under optimum conditions a hydrogen-enriched liquid product derived from coal by a novel combination 'of coal processing steps.

A still further object of the present invention is to Vprovide a process for converting coal to a hydrogen- Weight of the m.a.f. coal (m.a.f. signifies moisture-free 4and ash-free). A part of the extract consisting pre- 'dominantly of benzene-insoluble material is separated ffrom the extract. `coked alone or in combination with the undissolved 'portion of the coal, i.e. residue, to yield a benzene-sol- This benzene-insoluble fraction is uble product. All or selected fractions of the liquid 'products including the remainder of the extract are corn- 'bined and hydrogenated-to yield a high quality gasoline feedstock.

In the preferred embodiment of my invention, the solvent extraction treatment is controlled to yield an extract, under the extraction conditions, which amounts 'to less than 60 percent by weight of the m.a.f. coal. l 'have found it desirable in certain cases to subject the coal to solvent extraction conditions such that between 60 and 8O percent by weight of the m.a.f. coal is dissolved. However, in such cases it is necessary to sep- `arate sullicient benzene-insoluble material from the ex- -tract so that less than 65 percent by Weight of the Vm.a.f. coal is recovered as the benzene-soluble rich fraction, .as will be more fully explained hereinafter.

For a better and more complete understanding of my invention, its objects and advantages, reference should be had to the following detailed description and to the accompanying drawings in which:

FIGURE l is a graph showing the relationship of hydrogen transferred from solvent to coal to the depth of extraction;

FIGURE 2 is a schematic flow sheet of the preferred -embodiment of my invention; and

FIGURE 3 is a schematicow sheet of an alternative :embodiment of my invention.

VPreferred vembodiment Referring to FIGURE 2 of the drawings, comminuted coalis introduced into a stirred solvent extraction zone loconcurrentlywith 0.5 to 4.0 parts by weightrof a solvent. `The extraction zone 10 is adapted to confine ,the coal and the solvent for aresidence period from Aabout five minutes tofour hours at elevated pressures sired depth, of coal extraction. The pressure is that required to maintain the solvent as a liquid at the selected temperature, generally in the range ofV 1 p.s.i.g.

, Suitable solvents for the coal in the Yextraction step `are those which are predominantly polycy'clic hydrocar- The residence period and tempera- .tures are determined by the specific solvent and the deor mixtures thereof boiling between about 260 C. and 425" C. are preferred. Examples of suitable solvents are tetralin, decalin, biphenyl, methylnaphthalene, and dimethylnaphthalene. Other types of coal solvent may be added to the above-mentioned types for special reasons, but the resulting mixture should be predominantly of the types mentioned, i.e.should constitute more than 50 percent by weight of the solvent used. Examples of additive solvents are the `phenolic compounds, such as phenol, cresols and xylenols.

As stated above, the coal is comminuted, and preferably, but not necessarily, of a fluidizable size, for example -14 mesh Tyler Standard screen. Up to about 25 percentV depth of extraction, the coal particles retain substantially their original size; beyond 25 percent extraction, the particles undergo degradation.

The coal and the solvent are maintained in intimate contact within the extraction zone 10 until the solvent has dissolved the desired amount of coal, i.e. up to percent by Weight of the m.a.f.vcoal. At least l0 per- Vcent by weight of the m.a.f. coal should be dissolved since the extract below 10 percent is essentially benzenesoluble material and therefore does not require-the use of my process. To dissolve above about 40 percent of the m.a.f. coal, it is normally necessary that hydrogen be added to the coal. This is usually accomplished by employing hydrogen-transferring solvents such as tetralin or mixtures of hydrocarbons derived from intermediate or final steps of the process. I have found that as one increases the depth of extraction, the transfer of hydrogen increases rapidly (as is demonstrated by reference to FIGURE l of the drawings) such that if the depth of extraction exceeds 80 percent, :the over-all process becomes economically prohibitive in terms of the Vcost of the hydrogen required. Specically, at high depths of extraction, the hydrogen does not react exclusively with the new-formingv extract, but instead produces an increasing amount of gas which is of little value as compared to the extract. In FIGURE V1 the hydrogen transferred (wt. percent of m.a.f. coal) to the extract from the solvent is plotted against depth of extraction.

As previously stated, Ias one increases the depth of extraction, each additional increment of extract contalns a higher proportion of benzene-insoluble material. Thus, the deeper one extracts, the greater the amount of benzene-insoluble Ymaterial that must be separated from the extract. In order to minimize the amount of benzene-insolubles that must be separated, I prefer to conduct the 'solvent extraction under conditions to yield au extract amounting to less than 60 percent `by weight of the m.a.f. coal.

The temperature of the Vextraction zone should be an elevated temperature between about .100 C. and 500 C., but in no event high enough to cause appreciable coke formation. In some instances it may be desirable to conduct the extraction in stages at Vsuccessively higher temperatures untilthe desired depth of extraction is attained. Instead of a batch system, a continuous countercurrent system may be employed. The particular system used is not material to the practice of my invention. Y

'Following extraction, the mixture of solvent, extract, and residue is conducted rapidly, so as to avoid cooling of the mixture, through a conduit 12 to a stirred separa- -tion zone 14. The primaryu function of this zone is to 'separate theV extract into ay benzene-insoluble rich fraction and a benzene-soluble rich fraction. This separation may be accomplished by the addition to the separation zone 14 of a parallinicv solvent, e.g. hexane, in a volume ratio of the paranic solvent to the extraction solvent between 0.1 and 1.0. Alternatively, the temperature of the seperation zone may be lowered below the temperature employed in the solvent extraction zone. Depending upon the coal solvent employed, the temperature of extraction, and the depth of extraction, vthe act'of cooling Vto low temperature may precipitate most of the benzene-insoluble rich fraction, thereby dispen- -sing -with the -necessity of adding the precipitating parafiinic solvent. If a paranic solvent is used, I have found that the solvent is useful as an aid to the subsequent separation of the solids from Vthe liquid. it is important in any event .to have determined in advance the amount of benzene-insolubles in the extract so that the precipitation of the desired amount of the extract can be controlled. The larger the amount of benzene-insolubles in the extract, the larger is the -amount of precipitating solvent that must be added, or the greater is the difference in temperature between the extraction zone and the separation zone that must be maintained.

'From the separation zone 14 a mixture of liquid and -solids is discharged through a conduit 16 to a conventional -ty-pe filtration zone 18, or if desired a centrifuge. The solids are therein separated from the liquid. The liquid phase, consisting of a solution of the benzene-soluble rich fraction of the extract and solvents, i.e., the parainic solvent, if used, and the extraction solvent, is conducted through a. conduit 20, to a fractionation zone 22 wherein -the extraction solvent is recoveredand recycled through `a conduit 24 to the extraction zone 10; and the precipitating solvent, if used, is recovered and returned through a conduit 26 to the separation zone 14.

The benzene-soluble Vrich fraction of the extract is separately recovered and conducted through a conduit 28 to a hydrogenation zone 30, the operation of which will be 'hereinafter described. If desired, some or all of the extraction solvent, instead of being recycled to the extraction zone 10, Vmay be'used asa diluent for the benzenesoluble rich fraction in its passage through the hydrogenation zone.

As pointed out earlier, it may be desirable to dissolve up to 80 percent by weight of m.a.f. coal. Depending on `the coal employed, the solvent used, as well as other extraction conditions, there may be suliicient benzene- `soluble material present in the incremental extracts beyond 60 percent to justify its recovery. However, to recover this additional benzene-soluble material requires `substantial separation of the incremental benzene-insolu- 'ble material. I have found it to be necessary to separate atleast sufiicient benzene-insoluble material to ensure recovery of less than 65 percent of the m.a.f. coal as the lbenzene-soluble rich fraction.

The solids from the filtration zone 18, i.e. the residue andthe precipitated benzene-insoluble rich fraction of the extract, are discharged into a conduit 32 where they are picked up by a stream of recycle gas, air, or steam enter- Ainggtllrough a conduit 34 and are carried into a carboniuzation zone 36. It should be noted at this point that, if desired, the residue from the extraction zone may be separated vfrom the extract as by filtration prior to separating the extract into the benzene-soluble and benzeneinsoluble rich fractions. In such -a case the residue is vsent directly to the carbonization zone 36, and the extract is then introduced into the separation zone 14. The benzene-insoluble rich fraction may then be coked separiartely or introduced into the carbonization zone 36. AThe carbonization zone 36 may be any one of the well- ,known systems for carbonizing carbonaceous solids at low temperatures, i.e., 425 C. to 760 C. For example, a bed Aof solidsmay be maintained in the zone in a uidized state by means of the above-mentioned carrier gas. The temperature of the carbonization zone may be maintained ,by any suitable means, for example, by preheating the carrier -gas to the appropriate high temperature. I prefer, however, to burn a portion of the carbonized residue, i.e. char, produced in the carbonization zone 36 to supply the necessary heat. This is accomplished by withdraw- 'ing char from the carbonization zone 36 through a con- -duit 38, and conveying the withdrawn -char by means of an-inert gas such as recycle ga-s entering through a conduit 40 into -a char devolatilization zone 42. The cha-r is preferably maintained in a uidized state in this -zone at a vtemperature between about 645 C. and 945 C. The devolatilization temperature must be higher th-an any lprocessing temperature to which the solids `have been previously exposed. The volatile content of `the solids will be driven off as a hydrogen-rich gas which can be recovered through a conduit 44. A typical composition of such gas produced by simply heating char (derived by carbonization at 496 C.) at 870 C. is in percent by volume as follows: P12-72.0; ILS-0.75; CO2-0.81; (20-13.19; CHF-12.15; and N2--1.1. Devolatilization of char to produce hydrogen-rich gas is further described and claimed in my copending application, Serial No. 144,423, led October 11, 1961, which -is assigned to the assignee of the present application. A portion of `the devolatilized char is withdrawn from the devolatilization zone 42 through a conduit 46; picked up by air entering through a conduit 48, and lifted through a combustion leg 50. The temperature of the char as a result of the combustion is raised to that suic-ient to maintain the temperature in the devolatilization zone 42 when returned through a cyclone separator 52 and a conduit 54 to that zone. Flue gas is removed from the cyclone separator 52 through a conduit 56. Hot char from the devolatilization zone 42 is transferred by a conduit 5S back to the carbonization zone 36 by means of recycle gas from the conduit 40. Net char produced in the carbonization zone is discharged through a conduit 60. The hydrogenrich gas from the char devolatilization zone 42 is conducted via the conduit 44 to a conversion zone 62 where substantially pure hydrogen is produced by techniques well known in the yart. The resulting hydrogen is conveyed through a conduit 64 to a compressor 66 which compresses the hydrogen to the desired pressure. The compressed hydrogen is conducted to the hydrogenation zone 30 through a conduit 68.

Returning to the carbonization zone 36, the etiluent tar vapors are circulated through cyclone separators 70 and 72, which return finely divided solids to the carbonization zone 36. 'The tar vapors are conducted through -a conduit 74 to a condenser 76 where non-condensable gas is discharged through a conduit 78. The gas may -be used for manufacture of hydrogen by known methods such as steam reforming or vmay be used as plant fuel. The tar is carried through a conduit `Si) to a fractionation zone 82 in which a liquid fractionboiling below 325 C. and a liquid fraction boiling above 325 C. are recovered. The fraction boiling below 325 YC. is discharged through a conduit 84 which leads to the conduit 24 emptying into the extraction zone 10. If desired, however, a 'portion of the low boiling fraction may be recovered through a conduit 86 and thence introduced into a gasoline refining plant. The vfraction boiling above 325 C., after suitable treatment (not shown) to remove any solids, if present, is discharged into a conduit 88 which conveys the fraction `to the conduit 28 wherein it iscommingled with the benzene-soluble rich fraction.

The mixture of the benzene-soluble rich fraction .and the tar in conduit 28 contains asphaltic `materials or asphaltenes which have yan .average molecular weight be- .tween about 700 and 1000. In some instances it may he desirable to reduce the asphaltene content. Accordingly, a deasphalting zone 9 0 may be interposed lin the conduit Z8 for precipitating at least a portion ofthe asphaltenes. The deasphalting is accomplished by well-known methods employed in petroleum technology such as the addition of propane, pentane, or hexane. VThe precipitated asphaltenes, preferably diluted with a fluxing oil such as a portion of a coker distillate, are conducted through a conduit 92 to a preheater 94 and Vthence into a coking zone 96 adapted in conventional fashion to coke the asphaltenes at a temperature between Vabout 426 C. and 760 VC. Ash-free coke is discharged through a Conduit 9,8. vT he coker distillate is removed through a -conduit -100 and condensed in a condenser 102, from which norrcondensable gases are discharged through a conduit 104. The condensate is carried by a conduit 106 back to the conduit -28 leading to the hydrogenation zone 30. An added admay be.

Preferably, however, the mixture of benzene-soluble `rich extract and the tar from the fractionation zone 82,

recovered via the conduit 88, is introduced directly into the hydrogenation zone 30.

In the hydrogenation zone 30, the extract and tar are contacted with hydrogen, preferably in the presence of a hydrogenation catalyst. As previously mentioned, hydrogen is introduced into the hydrogenation zone 30 via the conduit 68; however, if required, additional hydrogen may be introduced into the system through a conduit 108 at the compressor 66. Hydrogenation of the extract and tar Vcan be conducted at pressures of 1000 p.s.i.g. to 10,000 p.s.i.g., preferably about 2000 p.s.i.g. to 3500 p.s.i.g., a range Well below that tnormally required for direct hydrogenation of coal. The hydrogenation temperature range is about 400 C. to 600 C., preferably about 410 C. to 455 C. The hydrogenation catalyst should be sulfur-resistant, eg., molybdenum or tungsten oxides or suldes impregnated on a refractory support to permit catalyst regeneration. The support usually will be an alumina-rich material such as pure gamma alumina or alumina composited with other oxides such as silica. lOther metals such as nickel or cobalt may be added as catalyst promoters.

The products of hydrogenation are discharged from the hydrogenation zone 30 through a conduit 110, cooled,

' and passed into a separator 112. Hydrogen-rich gas is separated from the products and recycled through a conduit 114 to the hydrogenation zone 30. The remaining products in the separator 112 are depressurized and then passed via a conduit 116 into a low pressure separator 118. From the low pressure separator 118 the liquid product is carried through a conduit 120 to a fractionation zone 122, while the gaseous product is withdrawn from the separator 118 via a conduit 124. The liquid product is fractionated in the fractionation zone 122 into any desired fractions. A preferred separation is to fractionate the liquid hydrogenation product into a fraction boiling above 360 C. and a fraction boiling below 360 C. The latter fraction is passed through a conduit 126 to further'rening yand hydrogenation operations for conversion to gasoline in conventional fashion. The former fraction is passed through a conduit 128 and may be reintroduced into the hydrogenation zone 30 or into the coking zone 96. IfV desired, portions of both fractions may be introduced into the solvent extraction zone 10, as a portion of the solvent therein.

EXAMPLE I MAF Coal, Extract,

Weight Weight Percent Percent Fr 5. 74 6. 45 s2. 26 s3. 51 N 1. 31 1. 23 8. 13 6. 81 t: 2. 56 2. 00

The yields of extraction products, based on 100 pounds of m.af. coal, are as follows:

Weight of product (pounds) Hydrogen sulfide 0.1 Gas 1.0 Liquor 1.0 Extract 23.0 Solid residue (maf.) -..74.9

The addition of 50 pounds of hexane to theextract solution precipitated 6.2 pounds of extract of which about percent by weight was determined to be benzene insoluble. The remainder of the extract contained about percent by weight of benzene-soluble material. The precipitated extract and solid residue were carbonized at 510 C., yielding 58.5 pounds of char and 12.6 pounds of tar including the light oil fraction. The total yield of liquid was thus 29.2 pounds.

In the description of the preferred embodiment, the deasphalting step (see of FIGURE 2) and the coking of the precipitated asphaltenes (see 96 of FIGURE 2) may be eliminated and, instead, the +360 C. oil from the hydrogenation zone 30 be recycled through that zone. Or as a still further option, the deasphalting stepvmay be eliminated with the +360 C. oil from the hydrogenation zone 30 going to the coker 96. In order to compare these three optional modes of treatment of the hydrogenation feedstock, the above-mentioned liquid yield of 29.2 pounds was divided into three aliquot Vparts which were respectively subjected to the three optional treatments.

The first aliquot part, hereinafter called Aliquot A, was treated in accordance with the steps shown in FIGURE 2, namely, as follows, with the understanding that the yields are reported on the basis of a starting feedstock of 29.2 pounds, that is, the actual yield is multiplied by three. To Aliquot A was added 20 pounds of hexane per 100 pounds of Aliquot A. The resulting precipitate comprising principally asphaltenic material amounted to 4.6 pounds. The latter was coked in a conventional delayed coking system at 470 C., yielding 2.7 pounds Vof ash-free coke and 1.4 pounds of coker distillate. The latter was combined with the non-precipitated portion of the extract from the deasphalting step, making a total of 26.0 pounds, which was then hydrogenated in a fixed bed catalyst system. The catalyst was cobaltmolybdate on alumina (15% MODs-3% COO-82% A1203); the temperature was 440 C.454 C., and the pressure 3500 p.s.i.g. The liquid hourly space velocity was about 1.0 pound of total feed per pound of catalyst per hour. The hydrogenated products were fractionated and the -360 C. distillate recovered as gasoline feedstock. VThe +360 C. fraction amounting to 10.4 pounds was recycled through the hydrogenation zone 30. The amount of H2 Vconsumed was 1.22 pounds. Y i

The second aliquot part, hereinafter designated Aliquot B, was simply sent directly tothe hydrogenation zone without any deasphalting or coking treatments. The same hydrogenation conditions were employed as used for Aliquot A. The hydrogenated products likewise were fractionated yielding 25.8 pounds of 360 C. gasoline feedstock and some +360 C. oil which was recycled through the hydrogenation zone. The amount of H2 consumed A was 1.46 pounds.

The third aliquot part, hereinafter designated as Aliquot C, like Aliquot B, was sent directly to the hydrogenation zone and hydrogenated under thesame conditions a's were the other aliquot parts. The resulting hydrogenated products were similarly fractionated into, a -360 C. fraction (23.5 pounds) and a +360 C. fraction (10.6 pounds). The latter was coked in the above-mentioned delayed coking system at 468 C., yielding 1.8rpounds of ash-free coke and 8.1 pounds of coker distillate which was mixed with Aliquot C before entering the hydrogenationzone, f Y.

9 The results of the above-described treatments may be summarized as follows:

TABLE HI Composztlon of the several feed materials H l kC N l O S Raw Extract -..--.1, 6. 45 83.5 1.2 6.8 2. 0 Extract with Benzene Insolubles Removed 69 83.1 1.0 7.2 2.1 Tar from Low Temperature Carbonization 7. 60 83.3 1.0 6. 5 1.6 Coker Distillate Aliquot A 7. 31 86.1 1. 0 4.2 1. 4 AverageRecycle Oil to Hydrogcnation one 9.07 89.9 0.4 5 0.1 Total Feed to Hydrogen (Excluding Recycle Oil) Aliquot A 7. 24 82. 9 0 9 7. 0 2. 0 Aliquote B and C-.- 7. 08 83.1 1 0 6.9 1. 9

TABLE 1V Feed composztion to hydrogenatzon zone and total yzelds Aliquot Aliquot Aliquot A B C Case Case Case W. Percent of Feed to Hydrogenation one:

Extract and Tar 71. 5 66. 7 78. 3 Recycle Oil 28.5 33.3 V21.7 Yield Wt. 'Percent of MAF Coal:

60 C. Distillate 23.2 25.8 23. 5 Gas 1.7 V1. 8 2.2 Liquor. 1. 9 2. 1 2. l H23 0.5 0.6 0.5 Ash-free Coke..- Y 2. 7 0.0 1. 8 Hz Consumptio 1.22 1. 46 1.34 Lbs. Hz Consumed per 100 lbs. of

-360 C. Distillate 5. 25 5. G6 5. 69

YEXAMPLE 2 Pittsburgh Sea-rn coal was subjected to a solvent extraction in a closed vessel with tetralin at a temperature of 380 C. for 52 minutes. Based on `100 pounds of maf. coa-l, 200 pounds of tetralin were employed. The yields of extraction products based on 100 pounds of maf. coal are as follows:

Weight of product (Pounds) Extract 68.3 Residue (maf.) 23.5 Gas-i-liquor-i-light oil 8.2

Precipitated Benzene- Extract, Soluble Percent Fraction,

Percent Benzene-solubles 3. 1 61. 2 Beuzene-Insolubles 96. 9 38. 8

Alternative embodiment An alternative embodiment of the present invention is illustrated in FIGURE 3 of the drawings. The chief distinction between the preferred embodiment and the alter- 10 `native embodiment lies in the treatment of Ythe extract, as the following description will show.

'Referring now to FIGURE 3, in order to avoid 11nnecessary duplication of description, those parts of the alternative embodiment operating the same as corresponding parts of the preferred embodiment have been designated by the Vsaine numerals. The mixture of extract and residue produced in the extraction zone 10 is con- -veyed through a conduit 11 to the filtration zone 1S where the extract is lseparated from the-residue. The latter is conveyed through a conduit 13 to a drying zone 15 wherein steam entering through a conduit 17 is employed to strip any retained solvent from the residue. The etiiuent stream from the dryer is passed through a conduit 19 to a pair of cyclone separators 21 which separate the vapors from the solids. The solids drop into a conduit 23 where they are picked up by recycle gas and introduced into the carbonization zone 36. The operation of this zone, together with the char devolatilization zone 42 and the char combustion leg 50, is the same as that described in connection with the preferred embodiment.

The extract is conducted through a conduit 25 to a dash tower 27 where at least some ofthe solvent fis flashed ott through a conduit 29. The solvent vapors are commingled with solvent vapors from the residue dryer 15 in a conduit 31 which carries them to a condenser 33. Any non-condensable gas is discharged through a conduit 35 while Ythe condensed solvent is Areturned to the extraction zone v10, via a conduit 37.

The extract is conveyed vfrom the ash tower 27 through a conduit 39 to a preheater 41 which serves t0 raise the temperature of the extract to about 426 C. to 468 C. The preheated extract is passed through a mild prehydrogenation zone 43 which serves to .add about 0.5 to 2.0 pounds of hydrogen pernlOO pounds of feed. The operating conditions are as follows:

Temperature: 425 C. to .470 C., preferred 440 C. to

Pressure: 5.00-2500 p.s.i.g.

Residence time: 5-60 minutes, preferred 10-30 minutes.

Hydrogen input to the prehydrogenator 43 may be by means of hydrogen transfer from hydrogenated middle oil derived from the final step of the present process. Free hydrogen gas may also .be added to aid hydrogenation. The operation is conducted substantially non-catalytically, or with relatively small amounts of "homogene- Tous catalysts, i.e., .05 to 1.0 weight percent of -a hydrogen halide or its .corresponding ammonium salt, ie., NH4C1, NH4Br, or NH4I. Inexpensive catalysts such ais red mud may also be Vused if desired. YThe hydrogenated middle oil is used in amounts 4between `1 ,and 3 parts per part of extract, preferably mixed with solvent from flash tower 27. Mild prehydrogenation of extract is further described and claimed in my copending application, Serial No. 144,428, tiled October 1l, 1961, which is assigned to the assignee of the present application.

The mildly hydrogenated extract is discharged through a conduit 45 into a fractionation zone 47 which serves to separate the extract into a +325 C. and a 325 C. fraction. The latter fraction is sent directly through a conduit 49 to the hydrogenation zone 30. The l-325 C. fraction is conveyed through a conduit 51 into a con duit 53 to a preheater 55 and thence through a conduit 57 to a coking zone 59 operating at 425 C. to 760 C. Ash-free coke s discharged through conduit 61. Coker distillate is withdrawn from the coking zone 59 via a conduit 63 and is commingled with the tar vapors withdrawn from the carbonizer 36 via a conduit 65. The mixture is then introduced into a fractionator 67. A -300 C. fraction is recovered through a conduit 69 for further refining, if desired, to yield chemicals and low boiling solvents. A 300 C. to 425 C. fraction is sent through a conduit 71 to a preheater 73 and thence rvia conduits 75l and 49 intoA the hydrogenation zone 30.

A +425 C. fraction is recycled through a conduit 77 to .the coking zone 59. The hydrogenated products from ,.thle hydrogenation zone 30 are lconveyed through a con- .duit '7,19 to the fractionator 122 and therein separated into gasoline feedstock recovered through the conduit 126 and amake-up solvent stream recovered through the conduit 128. n

According to the provisions of the patent statutes, I have explained the principle, preferred construction, and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope ofthe appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

p l. A combination process for the production of hydrogen-enriched liquid fuels from coal which comprises subjecting the coal to solvent extraction under conditions to dissolve less than 80 percent by weight of the m.a.f. coal, whereby an extract containing both benzene-soluble and benzene-insoluble material v is obtained, separating from the products of extraction undissolved coal residue and afiirst and a second extract fraction, said first fraction being richer in benzene-insoluble material than said second fraction and said second fraction amounting to less than 65 percent by Weight of the m.a.f. coal, subjecting said residue and said lrst extract fraction to carbonization under conditions yielding liquid distillates, combining at least a portion of said second extract fraction with at least a portion of said distillates, subjecting the result ing mixture to hydrogenation under conditions to yield a gasoline feedstock, and recovering said gasoline feedstock.

2. A combination process for the production and recovery of liquid hydrocarbons from coal which comprises subjecting the coal to solvent extraction in a solvent containing predominantly hydrocarbonsselected from the class consisting of polycyclic aromatic and polycyclic hydrogenated aromatic hydrocarbons and mixtures thereof under conditions to yield an extract amounting to less than 60 percent by Weight of the m.a.f. coal, adding a paranic solvent to the extraction mixture of solids and solution in suicient quantity to precipitate a portion of the extract which contains predominantly benzene-insoluble material, separating the extract solution from the coal residue and precipitate, adding a deasphalting solvent to the separated extract in sucient quantity to precipitate at least a portion of the asphaltenes, carbonizing coal residue, the precipitated benzene-insoluble portion and the asphaltene portion at 425 C. to 760 C., subjecting at least a portion of the liquid products from the aforesaid process steps to hydrogenation and recovering the resulting hydrogenated products.

3. A combination process for the production of hydrogen-enriched liquid fuels from coal which comprises subjecting the coal to solvent extraction under conditions to yield an extract amounting to less than percent by weight of the m.a.f. coal and containing both benzenesoluble and benzene-insoluble material, separating from the products of extraction undissolved coal residue and a first and a second extract fraction, said rst fraction being richer in benzene-insoluble material than said second fraction, subjecting said residue and said rst extract fraction to carbonization under conditions yielding liquid distillates, co-mbining at least a portion of said second extract fraction with at least a portion of said distillates, subjecting the resulting mixture to hydrogenation under conditions to yield a gasoline feedstock, and recovering said gasoline feedstock.

4. A combination process for the production of hydrogen-enriched liquid fuels from coal which comprises subjecting the coal to solvent extraction under conditions to yield an extract amounting to less lthan 60 percent by weight of the m.a.f. coal and containing both benzene,- soluble and benzene-insoluble material, separating from lthe products of extraction undissolved coal residue and a rst and -a second extract fraction, said first fraction being richer in benzene-insoluble material than said second fraction, further separating from said second extract fraction a third and a fourth extract fraction, the third fraction being richer in asphaltenes than the fourth fraction, subjecting said residue, said first extract fraction, and said third extract fraction to carbonization' under conditions yielding liquid distillates, combining at least a portion of said fourth fraction with at least a portion of said liquid distillates, subjecting the resulting mixture to hydrogenation under conditions to yield a gasoline feedstock, and recovering said gasoline feedstock.

5. A combination process for the production of hydrogen-enriched liquid fuels from coal which comprises subjecting the coal to solvent extraction under conditions to dissolve between 60 and 80 percent by Weight Vof the m.a.f. coal, whereby an extract containing both benzene- -Soluble and benzene-insoluble material is obtained, separating from the products of extraction undissolved coal residue and a'rst and a second extract fraction, said first fraction being richer in benzene-insoluble material than said second fraction, said second fraction comprising less than percent by weight Yof the m.a.f. coalsubjecting said residue and said first extract fraction to carbonization -under conditions yielding liquid distillates, combining at least a portion of said second extract fraction with at least a portion of said distillates, subjecting the resulting mixture to hydrogenation under conditions to yield a gasoline feedstock, and recovering said gasoline feedstock.

. No references cited. 

1. A COMBINATION PROCESS FOR THE PRODUCTION OF HYDROGEN-ENRICHED LIQUID FUELS FROM COAL WHICH COMPRISES SUBJECTING THE COAL TO SOLVENT EXTRACTION UNDER CONDITIONS TO DISSOLVE LESS THAN 80 PERCENT BY WEIGHT OF THE M.A.F. COAL, WHEREBY AN EXTRACT CONTAINING BOTH BENZENE-SOLUBLE AND BENZENE-INSOLUBLE MATERIAL IS OBTAINED, SEPARATING FROM THE PRODUCTS OF EXTRACTION UNDISSOLVED COAL RESIDUE AND A FIRST AND A SECOND EXTRACT FRACTION, SAID FIRST FRACTION BEING RICHER IN BENZENE-INSOLUBLE MATERIAL THAN SAID SECOND FRACTION AND SAID SECOND FRACTION AMOUNTING TO LESS THAN 65 PERCENT BY WEIGHT OF THE M.A.F. COAL, SUBJECTING SAID RESIDUE AND SAID FIRST EXTRACT FRACTION TO CARBONIZATION UNDER CONDITIONS YIELDING LIQUID DISTILLATES, COMBINING AT LEAST A PORTION OF SAID SECOND EXTRACT FRACTION WITH AT LEAST A PORTION OF SAID DISTILLATES, SUBJECTING THE RESULTING MIXTURE TO HYDROGENATION UNDER CONDITIONS TO YIELD A GASOLINE FEEDSTOCK, AND RECOVERING SAID GASOLINE FEEDSTOCK. 